A device for guiding the leading edge of a sheet to be folded in a folding machine

Abstract: Device for guiding the front edge of a sheet (1) to be multi-folded on itself having, parallel with the rectilinear path (2-3) of feeding of the sheet, an elastically flexible lamellar means (6). Such lamellar means (6) takes two positions, an operative position in which the lamellar means is moved forward to the outlet point of the sheet from the feeding path (2-3), the lamellar means end (15) being bent, with bending shape memory, at said outlet point of sheet (1) in the same directions the sheet front edge of the sheet is to be deviated to, to guide the latter towards a folding unit (10,7) and a rest position in which the lamellar means (6) is brought again to the initial retracted position in such a way that the bent part (15) of the lamellar means (6) does not hinder the movements of the sheets during the folding phase thereof.

Description: The present invention relates to a device suitable for guiding in a precise manner in a desired direction, in a paper sheet folding machine, the leading edge of a sheet to be multi-folded, accordion-like, onto itself, during the initial sheet folding phase, and to a folding machine provided with such a device. A folding machine for sheets having a considerable length and width, suitable for folding said sheets many times onto themselves in one or both directions so as to obtain an accordion-like or zigzag folded sheet, is described, for instance, in Italian Patent N° 2,083,484 and in the corresponding EP-A-0 171 486 of the applicant. The main problem in folding machines is to provide a means which can assure that the leading edge of the sheet to be multi-folded onto itself, be precisely directed towards the folding unit during the initial phase of forming the first fold. In actual fact if the leading edge is not guided in a precise and reliable manner in the desired direction and along the pre-established path, the subsequent folds, will be faulty, namely they will show dog-eared corners, wrinkles or other defects due to the leading edge of the sheet to be folded having, in the initial phase, possibly hit againts an element of the folding unit or other undesired obstacle. Such problem was solved, both in the above-mentioned patents and in other folding machines, in a more or less satisfactory manner. In EP-A-0 171 486 of the Applicant, the content of which is incorporated herein by reference, the device for directing in a precise way the leading edge of the sheet consists of a roller RO located in the advancing path of the sheet to be folded. Said roller, rotating in the feed direction of the sheet, cooperates in directing in a precise manner the leading edge of the sheet towards the first folding phase, thereby avoiding right from the start undesirable folds. Immediately afterwards the roller RO is shifted into its lower position so as not to hamper the subsequent folding phases, while it must return to its original position at the start of the folding of a new sheet. This device, though solving this problem in a satisfactory manner, is very costly inasmuch as it implies a fairly complex mechanical solution in order to move, alternatingly and rapidly, a heavy mass such as that constituting of roller RO, of its pivot and of its driving organs, and it demands frequent servicing. As it is known, sheet folding machines work at a very high speed. The object of this invention is therefore to solve such problem in a simpler, less expensive, and most of all more reliable manner. This object is achieved by the features of the characterising portion of claim 1 so the sliding laminae means directs in its operative position in a precise manner the leading edge of the sheet to be folded in the desired direction and in the required position during the initial phase of forming the first fold, without any possibility of undesired deviations and without encountering hindrances that might result in the formation of the dog-eared corners in the sheet leading edge. Subsequently said laminae means is retracted to a non-operative position, outside the sheet stacking area for the formation of folds, and the folding operation proceeds in the conventional manner, imparting to the sheet, in succession, the different folds as required. This laminae means is made of an appropriately shaped, resiliently flexible material which is endowed with shape memory. The laminae means is moved forwards, parallel to the sheet to be folded, in a continuous manner, from a retracted position in an appropriate stationary slide assembly, which is parallel to the sheet advancing path, until said laminae means reach an area between the folding unit wherein the sheet is to be accumulated in order to form in it bends preliminary to the forming of the folds. The resiliently flexible laminae means has its end protruding from the slide assembly in a curved shape, to said end having moreover been imparted a shape memory in respect of said bending, the curved shape of the laminae means allowing a reliable guide action for the leading edge of the sheet to be folded which is directed towards the first folding station, whereafter the laminae means is moved backwards and sheltered in its slide assembly, while the remaining part of the sheet is subsequently folded repeatedly onto itself, as needs be in a per se known manner. The use of the laminae means simplifies the construction of the folding machine, thus rendering it less costly and easier to service over the prior art solutions. The mass of the laminae means, according to the instant invention, which has to be shifted at the start of each new folding operation, is much less than that of a roller, of its pivot and of its related operating organs according to the prior art. The alternating method of entry and exit of the laminae means, from and into its slide assembly, is mechanically realizable in a relatively simple manner and as a result of the lesser mass of the laminae means, rapid movements of the folding machine can be performed with the necessary promptness. The forward and backward movements of the resiliently flexible laminae means may be carried out by means of various prior art drives and an embodiment of this invention may consist of a T-shaped, fixed geometry rocker lever, the vertical rod of which, corresponding to the T stem, is articulated on a cross arm to which is connected the end of each one of the flexible laminae means, which cross arm is opposite to the resiliently bent operative end of the laminae, the latter acting as a guide element for the leading edge of the sheet to be folded. The opposite end of said vertical rod is pivoted, similarly to a first class lever fulcrum, on the central part of a cross-rod of the rocker lever, one end of said cross-rod of the rocker lever being actuated by a drive system for the advancement of the flexible laminae means, and the other one being biased upon by an antagonistic means moving the laminae means to the retracted position in the slide assembly for the laminae means. To better understand the invention, the same will be described and illustrated hereinbelow, exemplarily referring to a schematic, non limiting, embodiment as shown in the attached drawings, where: Figures 1, 2 and 3 are schematic vertical elevation views, showing three different operational phases of a folding machine, namely an initial phase of an operative cycle, said cycle after a first reversal condition of the folding unit, and said cycle after a second reversal condition of the folding unit, to obtain an accordion-like or zigzag folded sheet, respectively; and Figure 4 is a schematic top view of the laminae means, according to the invention, made of a resiliently flexible material, in combination with a sheet feeding or advancing roller means consisting of a plurality of separate small rollers. A folding machine of the type disclosed in the aforecited patents will first be described in a schematic form, machine which is provided with resiliently flexible laminae means according to the present invention for precisely guiding the advancement, in the desired direction, of the leading edge of the sheet to be folded. The sheet to be folded accordion-like is indicated in Figures 1-3 by the reference numeral 1 while wound over itself like a roll. A first section of said sheet is passed within an advancing path consisting of an upper plate 2 and a lower plate 3. Said sheet, is drawn by an upper roller 4 and a lower roller 5, constituting a feeding unit one of which roller being the driving roll, and it proceeds until it exit through the outlet end 2' of said plates 2 and 3. At this stage, were there not the laminae means 6 according to the present invention or any other known sheet directing system, the sheet, continuing its advancing movement, would proceed until it hits against the left section 7' of a continuous tape 7 rotating around two drums, a lower one 8 and an upper one 9, of a folding unit also comprising upper roller 10 and lower roller 11. Drums 8 and 9 are rotated in known manner alternatingly in a clockwise and counter-clockwise direction, as will be explained hereinafter; therefore, when they rotate in a clockwise direction, the left section 7' of the tape has an upward movement, whereas when they are rotated in a counter-clockwise direction said left side section has a downward movement. In Figure 1, representing the initial folding phase, said left tape section 7' has an upward movement, and therefore the tape front edge, as a consequence of the upward movement of continuous tape 7, left section 7', tends to be directed upwards as shown in Figure 1, subsequently being compressed and then held between the first upper folding roller 10 and the left section 7' of the continuous tape 7 of folding unit 7, 10, 11. While the sheet advances and under reversal of the rotation of drums 8 and 9, one of which is the driving one, and the other idle, an excess of the sheet material is accumulated (Figure 2) in the space between said upper roller 10 and lower roller 11 and the left tape section 7', whereby a bend 12 is formed in the sheet 1. Such bend 12 proceeds downwards as the sheet advances until it passes between the tape left section 7' and the lower folding roller 11, until a first fold 13 is formed in the sheet (Figure 3). The cycle is then repeated with a further reversal of the movement of tape 7, so as to form various folds in the sheet. All this is already known from the aforecited patents. Therefore it is necessary to provide a device for initially driving upwards in a precise manner the leading edge of the sheet, in the direction towards the first folding roller 10, when such sheet leading edge, in the starting phase shown in Figure 1, engages the left section 7' of continuous tape 7 in order to prevent that an undesired downward bend, or dog-ear, be formed. In order to avoid this drawback, a somewhat complex and costly mechanism was provided for in the aforecited prior art patents. According to the present invention, laminae means 6 (Figure 4), made from a resiliently flexible material susceptible to be shaped in a permanent way, namely with shape memory, such as for instance harmonic steel or suitable synthetic resins, is mutually connected by means of a cross arm 14. The opposite end of said laminae means 6, indicated by 15, is bent upwards in a permanent way, which is to say with a memory of such bent shape, in the direction towards the upper folding roller 10, passing through an appropriate slide assembly consisting of said lower plate 3 and by a further lower plate 16. The cross arm 14 is articulated on a rocker lever member 17 consisting of a vertical rod 18 and a cross rod 19 which is pivoted at 20. One end of the cross rod 19 of the rocker lever member 17 is connected to a traction element such as for instance an electromagnet 21, while the other end of cross rod 19 of the rocker lever 17 is joined to a return member, such as for instance a spring 22. The operation of the device according to the invention is described hereinbelow. At the start-up phase as shown in Figure 1, the electromagnet 21 is energized, so that the rod 18 of the rocker lever 17 swings in clockwise direction, reaching the position indicated in this Figure. By such movement the laminae means 6 is caused to move forward to the slide assembly consisting of plates 3 and 16, whereby their end 15, which is resiliently bent, is situated in the space between the folding rollers 10 and 11 and the tape 7, namely in the position in which the sheet leading edge exits from its path between plates 2 and 3 and is directed in a precise manner upwards, before engaging tape 7. At this stage, since the sheet leading edge has been positively directed upwards, the laminae means 6 is caused to be retracted, temporarily straightening out, into the rectilinear slide assembly consisting of plates 3 and 16, due to the de-energization of the electromagnet 21, whereupon spring 22, acting on the other end of cross rod 19 of the rocker lever 17, causes the vertical rod 18 to swing towards the left side (Figure 2), thereby causing the backward movement of laminae means 6 to a retracted position inside the slide assembly 3, 16, in a temporarily straightened condition. With the laminae means 6 retracted inside its assembly, the folding cycle proceeds, as previously explained, under reference to folding machines known from the aforecited prior art patents. It is evident that laminae means 6, owing to their flexibility, can easily revert to a straight shape when retracted into their slide assembly and, owing to their shape memory, they will be ready to take up their shape again, i.e. curved at their free operating end, as soon as they have again been pushed out of their slide assembly as a consequence of electromagnet 21 being energized, at the initial phase of insertion of a new sheet to be folded accordion-like. So far for convenience the various rotating elements that cause the paper advancement, its folding and its pressing into a folded condition were considered as integral elements; as a matter of fact such elements consists of several contiguous elements. For instance, tape 7 consists of a series of belts arranged side by side and, as it may be taken from Figure 4, the laminae means 6 passes through a series of small rollers 23, that in their entirety constitute roller 5, said rollers 23 being spaced apart from one another and mounted on a common shaft 24, that can for instance be a driving shaft. The structure of the element which causes the forward and backward movement of the laminae means, herein exemplified as rocker lever member 17, may be replaced by any device that is suitable for this purpose, and the same applies to the rocker lever control system, here consisting of an electromagnet and a spring, that may be replaced by any other known control system suitable for this purpose.

Claims: A device for precisely guiding in the desired direction, the leading edge of a sheet (1) to be multi-folded accordion-like on itself in the initial folding phase, performed by a sheet folding machine, the folding machine including rollers (4, 5) for feeding, along an advancing path (2, 3), a sheet to be folded, and a folding unit (7, 10, 11) to fold the sheet many times onto itself, characterized in that in parallel relationship with the rectilinear advancing path (2, 3) of the sheet to be folded, there is provided a resiliently flexible laminae means (6), with a resiliently bent outer end (15), at a position adjacent to and below the sheet to be folded, said laminae means (6) sliding in an own slide assembly (3, 16) parallel to said sheet advancing path, said laminae means assuming two positions: an operative one in which the laminae means (6) is caused to move forwards beyond the outlet point (2') of the sheet from its advancing path, the end (15) of the laminae means (6) at said outlet point (2') of the sheet (1) being bent due to its shape memory of bending in the same direction in which the sheet leading edge is to be initially oriented in order to guide at the start the latter towards the folding unit (7, 10, 11), and a second non-operative or rest position in which said laminae means (6) is returned to its initial retracted position in such a manner that the outer portion of the laminae means (6), retracted into its slide housing (3, 16), does not hinder the movements of the sheet (1) in the folding phases, the forward and backward movement of said laminae means (6) being caused by a rocker lever member (17) actuated at the initial phase of insertion of a new sheet. A device according to claim 1, characterized in that the laminae means is made of a material suitable for being shaped with shape memory, at one end of which laminae, a bent shape was imparted which is permanently maintained. A device according to claim 2, characterized in that said laminae means, at the end opposite to the bent end (15), is connected with a cross-arm (14) on which a rocker lever member (17) acts to move the laminae means (6) to the retracted position and to the projecting position towards the sheet folding unit (7, 10, 11). A device according to claim 3, characterized in that the rocker lever member (17) for the forward and backward movement of said laminae means consists of a T-shaped rigid piece, the vertical rod (18) of which, corresponding to the stem, is articulated on the cross arm (14) of the set of laminae, while the center (20) of the cross rod (19) of the T piece is pivoted on the relevant fixed structure of the folding machine in a first class lever fulcrum-like manner, one end of the cross rod (19) of the rocker lever (17), closest to the folding unit, being connected to a traction element (21) exerting a traction force on said one end, while the other end of said cross rod (19) is connected to a return member (22). A device according to claim 4, characterized in that the traction element (21) connected to one end of the cross rod (19) is an electromagnet while the return member (22), connected with the other end of the cross rod (19), is a spring. A device according to claims 1 to 5, characterized in that the laminae means consist preferably of several adjacent elements.

Inventors: RIGOLI VITTORIO, RIGOLI, VITTORIO
Applicants: RIGOLI F I M E S P A, RIGOLI F.I.M.E. S.P.A.
Application year: 1994
Main classification: B65H45
IPC codes: B65H45